1. Field of the Invention
The present invention relates to an electro-acoustic transducer.
2. Description of the Related Art
An ultra-thin, flexible speaker (also called a paper-thin, flexible speaker or an electrostatic speaker) has a first electrode, a second electrode, and a vibratile, thin metal film substrate, which carries positive charges and is disposed between the first electrode and the second electrode. When positive charges are transferred to the first electrode and negative charges are transferred to the second electrode, the metal film substrate moves away from the first electrode but closer to the second electrode; however, when negative charges are transferred to the first electrode and positive charges are transferred to the second electrode, the metal film substrate moves closer to the first electrode but away from the second electrode. When the changes of the electric polarities of the first and second electrodes continue, the metal film substrate will vibrate, compress air, and produce sound waves.
The vibratile, thin metal film substrate can be obtained by vapor-depositing an electrically conductive metal layer on a Mylar substrate. Charges are transferred to the thin metal film in order to carry charges.
It is insufficient to only use small audio electric signals to generate useful forces of electrostatic attraction and repulsion to drive a thin flexible speaker. Normally, a voltage booster is needed to amplify the audio frequency signals, which then increasing their voltage levels. Unfortunately, the danger of electric shock may be caused by such high voltages.